In a cellular mobile radio system, the fixed network part of the system is organized as a plurality of radio cells. During a communication transaction, a mobile station which is initially in communication with one radio cell may change cells by means of a handover process that ensures the orderly transfer of the communication transaction between cells. Within the fixed network part, a handover may result in a change in signaling path handling the passing of signaling messages to and from the mobile station.
For a variety of reasons, a network operator may be interested in following a communication transaction; for example, the operator may wish to find out how many transactions involve handovers or to associate pieces of information separately occurring during a transaction (such as the identity code given at the start of a transaction with a subsequently-assigned temporary identity code).
Of course, as part of its normal operation, the fixed network infrastructure follows communication transactions across handovers. However, as a practical matter, making this process or resultant derived information directly available to the network operator would requires substantial modification to existing infrastructure software with the consequent need to re-qualify the software and associated systems.
It is therefore an object of the present invention to provide a way of tracking communication transactions across handovers without requiring modification of the existing network infrastructure.
As will be more fully set out below, the present invention involves providing a monitoring method and apparatus that effects the desired following of transactions across handovers by monitoring signaling messages. Monitoring signaling messages is not new in itself and may be done using, for example, the Hewlett-Packard 37900D Signaling Test Set. However, as already noted, a handover may result in a change in signaling path carrying the signaling messages relevant to a transaction being followed; as a consequence, following a transaction across a handover requires substantially more than just monitoring messages on a single signaling path.